Timedependent projected HartreeFock
Abstract
Projected HartreeFock (PHF) has recently emerged as an alternative approach to describing degenerate systems where static correlation is abundant, when the spinsymmetry is projected. Here, we derive a set of linearized timedependent equations for PHF in order to be able to access excited states. The close connection of such linearresponse timedependent PHF (TDPHF) to the stability condition of a PHF wave function is discussed. Expanding this analysis also makes it possible to give analytical expressions for the projected coupling terms of Hamiltonian and overlaps between excited Slater determinants. TDPHF with spinprojection (TDSUHF) and its TammDancoff approximation are benchmarked for several electronically degenerate molecules including the dissociating H{sub 2}, F{sub 2} and O{sub 3} at equilibrium, and the distorted ethylene. It is shown that they give consistently better descriptions of excited states than does timedependent HF (TDHF). Furthermore, we demonstrate that they offer not only singly but also doubly excited states, which naturally arise upon spinprojection. We also address the thermodynamic limit of TDSUHF, using noninteracting He gas. While TDPHF singly excited states tend to converge to those of HF with the size of the system due to the lack of sizeextensivity of PHF, doubly excited states remain reasonable even atmore »
 Authors:
 Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States)
 Publication Date:
 OSTI Identifier:
 22415551
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BENCHMARKS; CORRELATIONS; COUPLING; EQUILIBRIUM; ETHYLENE; EXCITED STATES; HAMILTONIANS; HARTREEFOCK METHOD; HYDROGEN; MOLECULES; OZONE; SLATER METHOD; SPIN; STABILITY; SYMMETRY; TIME DEPENDENCE
Citation Formats
Tsuchimochi, Takashi, and Van Voorhis, Troy, Email: tvan@mit.edu. Timedependent projected HartreeFock. United States: N. p., 2015.
Web. doi:10.1063/1.4914511.
Tsuchimochi, Takashi, & Van Voorhis, Troy, Email: tvan@mit.edu. Timedependent projected HartreeFock. United States. doi:10.1063/1.4914511.
Tsuchimochi, Takashi, and Van Voorhis, Troy, Email: tvan@mit.edu. 2015.
"Timedependent projected HartreeFock". United States.
doi:10.1063/1.4914511.
@article{osti_22415551,
title = {Timedependent projected HartreeFock},
author = {Tsuchimochi, Takashi and Van Voorhis, Troy, Email: tvan@mit.edu},
abstractNote = {Projected HartreeFock (PHF) has recently emerged as an alternative approach to describing degenerate systems where static correlation is abundant, when the spinsymmetry is projected. Here, we derive a set of linearized timedependent equations for PHF in order to be able to access excited states. The close connection of such linearresponse timedependent PHF (TDPHF) to the stability condition of a PHF wave function is discussed. Expanding this analysis also makes it possible to give analytical expressions for the projected coupling terms of Hamiltonian and overlaps between excited Slater determinants. TDPHF with spinprojection (TDSUHF) and its TammDancoff approximation are benchmarked for several electronically degenerate molecules including the dissociating H{sub 2}, F{sub 2} and O{sub 3} at equilibrium, and the distorted ethylene. It is shown that they give consistently better descriptions of excited states than does timedependent HF (TDHF). Furthermore, we demonstrate that they offer not only singly but also doubly excited states, which naturally arise upon spinprojection. We also address the thermodynamic limit of TDSUHF, using noninteracting He gas. While TDPHF singly excited states tend to converge to those of HF with the size of the system due to the lack of sizeextensivity of PHF, doubly excited states remain reasonable even at the thermodynamic limit. We find that the overall performance of our method is systematically better than the regular TDHF in many cases at the same computational scaling.},
doi = {10.1063/1.4914511},
journal = {Journal of Chemical Physics},
number = 12,
volume = 142,
place = {United States},
year = 2015,
month = 3
}

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